Method for the transmission of a sensor data signal and an additonal data signal from a sensor component to a least one receiver

ABSTRACT

A method for the transmission of sensor data from a sensor assembly to one or more receivers is presented, in which, in response to a control signal, additional data are transmitted at least temporarily for a short time instead of the sensor data, whereby only a certain limited value range of the value range that is available for the sensor data transmission is used for the transmission of the additional data, so that even with receivers which do not recognize that the transmitted data are additional data, erroneous functions or malfunctions are to be excluded. Thus, especially that value range of the sensor data signal that is to be attributed to a noise of the quantity to be measured or of the sensor assembly and is therefore not evaluated by the receiver in the normal signal operation, is used for the transmission of the additional data. In occupant protection systems, the safety-uncritical value range of a sensor data signal, which leads to no triggering of the occupant protection system, can correspondingly be used for the transmission of the additional data.

[0001] The invention relates to a method for the transmission of asensor data signal and an additional data signal from a sensor assemblyto at least one receiver.

[0002] Typically, a sensor measures a certain physical quantity andgenerates a corresponding sensor data signal, which is transmitted froma data transmission unit of the sensor assembly to the receiver, andthere, an application unit allocated to the receiver of the sensor datasignal is controlled dependent thereon. If, in addition to the sensordata signal, further data, be they control signals for controlling thedata transmission or additional or auxiliary data, are to betransmitted, then a different value range of the data signal can be usedfor this purpose, thus, for example, a higher amplitude for analogsignals, or a reserved bit value range for digital signals. As analternative thereto, there is a possibility of a multiplex operation, inwhich the value range of the sensor data signal can be used for theadditional data signal. In all cases, however, in addition to the sensorassembly as a transmitter, respectively also all of the receivers mustrecognize this data transmission protocol or the respective type ofoperation. Especially in sensor data bus systems, in which a pluralityof sensor assemblies and receivers are connected together on a bus,therefore an adaptation of all bus participants is necessary, even ifsuch additional data are to be exchanged between only a fewparticipants. A utilization of assemblies of an older generation, i.e. adownward compatibility, is thus excluded. Otherwise, error functions ormalfunctions could arise in the receiver or in the application unit,with respect to receivers which do not recognize that the transmitteddata are additional data signals.

[0003] Such sensor data bus systems are, for example, used in motorvehicles for the acquisition of safety relevant sensor data signals forthe controlled activation of occupant protection devices.

[0004] In this context, for example, if additional data signals would betransmitted instead of acceleration data signals, and a receiver of anoccupant protection device would not recognize this, either because itjust did not receive a corresponding control signal due to aninterference, or because it is not at all prepared for such atransmission of additional data signals, then there exists the danger ofthe erroneous triggering of the occupant protection device.

[0005] It is the object of the invention to present a method for thetransmission of a sensor data signal and an additional data signal froma sensor assembly to at least one receiver, in which erroneous functionsor malfunctions in the receiver are to be excluded. This object isachieved by the features of the claim 1. Advantageous furtherembodiments are to be seen from the dependent claims.

[0006] In that context, the basic underlying idea is to use, for thetransmission of the additional data signals, only that value range ofthe sensor data signal that is uncritical for the control of theapplication unit, whereby a receiver of the sensor data signal, whicherroneously interprets the additional data signal as a sensor datasignal, will not exhibit any significant erroneous functions ormalfunctions.

[0007] Thus, an often very considerable portion of the sensor datasignal value range, and therewith the transmission capacity, isknowingly dispensed with, for the benefit of the achieved functionalsecurity. For this, basically for nearly all data signals, the noiserange is always available, namely the value range of the sensor datasignal that is attributable to a noise of the quantity to be measured aswell as of the sensor assembly. Therefore, this noise range is notevaluated by typical conventional receivers. The useable range of thisnoise range is in turn limited downwardly only with analog signals dueto the noise component additionally arising on the transmission path,which naturally does not apply for digital signal transmission.

[0008] Moreover, however, dependent on the respective application, avalue range of the sensor data signal can additionally arise, in whichsimilarly no erroneous function or malfunction or fault will occur inthe respective application, if additional data signals are transmittedinstead of sensor data signals.

[0009] This is, for example, the case in such applications in which thesensor data signals are compared with a threshold value and theapplication unit is only activated for sensor data signals above thethreshold value. The usable sensor data signal value range in thiscontext is often considerably larger than the noise range.

[0010] A preferred application example arises for a sensor assembly inan occupant protection system for motor vehicles, in which the sensorassembly measures a safety relevant quantity and generates a sensor datasignal corresponding to the safety relevant quantity, whereby at leastone activation unit of at least one occupant protection device isprovided, which receives the sensor data signals and decides about thetriggering of the occupant protection device(s) dependent on this sensordata signal. In this context, the sensor data value range of the sensordata signal comprises a safety-uncritical value range in which theactivation unit does not initiate an activation of the occupantprotection devices. Therefore, exclusively this safety-uncritical valuerange is used for the transmission of the additional data.

[0011] In the following, the invention shall be further explained indetail in connection with example embodiments and Figures. Shortdescription of the Figures:

[0012]FIG. 1 sensor assembly connected to a sensor bus for thetransmission of a sensor data signal as well as an additional datasignal;

[0013]FIG. 2 value range of an analog sensor data signal and of ananalog additional data signal;

[0014]FIG. 3 digital code word value range for sensor data signal andadditional data signal of an acceleration sensor assembly;

[0015]FIG. 4 structure of the entire data protocol.

[0016] The FIG. 1 shows a sensor assembly 1, which transmits a sensordata signal s11 of a sensor data unit 11, i.e. the actual sensorfunction, to at least one receiver 2, which controls an applicationunit, which is not shown in detail, dependent on the sensor data signals11. Here in this example, an acceleration sensor assembly transmitsacceleration data signals to an activation unit of an occupantprotection system.

[0017] An additional data signal s14 stored in an additional data memory14 of the sensor assembly is also to be transmitted via the sametransmission channel 4.

[0018] In this example as a starting point, it shall be understood thatthe receiver 2 is a typical conventional activation unit of an occupantprotection system and is not prepared for the reception of additionaldata. In this example, a central unit 3 as well as a read-out unit 5,which is externally connectable via a contact and which serves forreading out the additional data, are also connected with thetransmission channel 4.

[0019] In response to a control signal, which here originates as s5 fromthe read-out unit 5, an additional data signal s14 is transmitted atleast temporarily for a short time instead of the sensor data signals11. The receiver 2, which is not prepared for the reception ofadditional data, will consequently interpret this. additional datasignal s14 as a sensor data signal and will evaluate it as such.However, only the value range that is uncritical for the control of theapplication unit, here the occupant protection device, is used as thesignal value range for the additional data signal s14, so that thereceiver 2 is not interrupted or interfered with thereby. On the otherhand, the read-out unit 5 can receive and evaluate the additional datasignal as such.

[0020] The control signal for the switching over (12) from the sensordata signal s11 to the additional data signal s14 can also be generatedby the central unit 3 in the form of a signal s3, for example when thisunit requires the additional data, whereby the type of the controlsignal does not necessarily have to be a digital data signal, which istransmitted explicitly and solely for this purpose, but rather, acontrol signal for still other functions can also be used, or such acontrol signal for the switch-over switch 12 can arise from certainfunctional or operating conditions, for example an interrupt or apower-on.

[0021] Moreover, the control signal can also be generated by the sensor1 itself, if, for example, this sensor always transmits the additionaldata in response to an internal reset of the sensor assembly, forexample after a power-on, or in a fixed time rhythm prescribed by meansof a control unit 16, or if applicable also an adjustable fixed timerhythm.

[0022] Moreover, it is also conceivable to provide a request orinterrogation by a receiver 2.x of an application unit, which is alreadyset up for the reception of additional data signals.

[0023] Thus, the manner of the incitation or initiation of theswitching-over to the transmission of the additional data signal s14instead of the sensor data signal s11 can be very flexibly adapted forthe respective application situation.

[0024] The data transmission unit 13 of the sensor assembly 1 as apreferred embodiment further comprises a monitoring unit 15, whichdetects the present actual values of the sensor data signal s11 at leastduring the transmission of the additional data signal s14, comparesthese present actual values with prescribed nominal or rated values, andupon exceeding these nominal or rated values terminates the transmissionof the additional data signal s14 and switches to the transmission ofthe sensor data signal s11, in other words automatically again switchesover the switch 12. Thereby it is ensured that no sensor data signalsthat are determinative or significant for the control of the applicationunit become lost during the transmission of additional data.

[0025]FIG. 2 sketches, in the manner of an example, the value range ofan analog sensor data signal x0 to xn, whereby the value range x0-x1corresponds to the noise range of the sensor data signal, which is to beattributed to a noise of the quantity to be measured as well as of thesensor assembly.

[0026] This noise range x0-x1 is therefore not evaluated by the receiver2, for example is eliminated by comparison with a lower threshold. Thisnoise range is thus completely unmeaningful for the control of theapplication unit and therefore uncritical.

[0027] Therefore, this noise range of x0-x1 is used as the signal valuerange y0-ym for the analog additional data signal s14 that is to betransmitted, so that the receiver 2, which, of course, cannotdistinguish the sensor and additional data signals from each other, onlyrecognizes a negligible noise therein. The read-out unit 5, however, isexactly optimized to this signal range, which is typically the lowersignal range for analog signals, and can therefore receive theadditional data signal s14. The value range of 0 to x0 lying therebelowis not utilized, due to a possible noise on the transmission channel inthe analog signal transmission.

[0028] On the other hand, if an application is present, in which thereceiver 2 compares the sensor data signal s11 with a threshold valuex2, and only activates the application unit for a sensor data signal s11exceeding the threshold value x2, the value range below this thresholdvalue x0-x2 can be used as the signal value range y0-ym2 for theadditional data signal s14. This expanded utilization of the sensor datasignal value range is possible for a plurality of application units inthat context, especially for failure or fault diagnosis devices that areonly active upon the occurrence of an error or fault, for accident orcrash sensors, which also must only activate certain application unitsupon or following a threshold value, whereby the threshold value x2 andthe quantity of the additional data signals s14 to be distributedthereupon are defined in an application specific manner.

[0029]FIG. 3 shows a method in which the data transmission of the sensordata and the additional data is carried out in digital code words. Here,the code words are formed in the manner of an 8-bit sequence, whichcorresponds to 256 code words. Due to the application specificpeculiarity of the sensor data signal to be transmitted, here of anacceleration signal provided with a sign, the code words are notrepresented from 0 to 256, but rather from −128 to +127, which, however,is initially unimportant or not meaningful for the method.

[0030] Of the quantity of 256 code words, one portion, here from +127 to+120 as well as from −121 to −128, is provided for the transmission ofcontrol signals, and the other portion from +120 to −120 is provided forthe transmission of sensor data. Moreover, of the code words (+120 to−120) used for the sensor data transmission, in turn a portion thereofcorresponds to sensor data that are uncritical for the control of theapplication unit, here due to particularly strict requirements these arelimited to code words from +3 to −3. Only this portion of the code wordsis used for the transmission of the additional data.

[0031] In this example in FIG. 3, namely the sensor data signal of anacceleration sensor are to be transmitted, whereby corresponding valuesof the acceleration are allocated to the code words +120 to −120, thusthe earth's gravitational acceleration g just corresponds exactly to thecode word 1. In this context, acceleration sensors typically acquire ordetect their values with a sign, which is also especially important forthe evaluation in the field of the crash recognition for the control ofoccupant protection systems. Thus, the portion of the code words usedfor the transmission of the additional data corresponds exactly once tothe range from +3 g to −3 g, namely an extremely small accelerationsignal value range that is uncritical for the crash recognition. In thiscontext, however, a particularity of the crash recognition has stillfurther been taken into consideration, namely that the activation unit,for deciding about the activation of the occupant protection device(s)carries out an integration of the acceleration signal and a comparisonof the acceleration integral signal with an activation threshold. Thisintegration namely has as a result that upon a repeated transmission ofthe respective largest values of a value range, these largest values asthe acceleration signal itself will not yet reach a triggeringthreshold, but the acceleration integral signal resulting therefromcould, however, quite well reach the activation threshold.

[0032] The safety-uncritical value range that is used for thetransmission of the additional data is therefore determined so that evenwith an integration of the largest values from the safety-uncriticalvalue range, the activation threshold will not be reached under anycircumstances, and finally it is ensured, that the data transmissionunit transmits the additional data signal s14 while using exclusively asafety-uncritical value range (x0-x1 corresponds here to +3 g to −3 g),in that an activation of the occupant protection devices by a receiver,which takes the additional data to be sensor data, is excluded.

[0033] In this example the method is used to interrogate or to transmitsensor production data, especially an individual sensor assembly number,with each reset of the sensor. Since the sensor production data are,however, relatively extensive or voluminous, it is necessary to carryout a transmission of the additional data in a sequence of several codewords.

[0034] In order to once again avoid errors or faults in that context,the use of position numbers is necessary, so that in addition to theactual additional useful data also these additional control data must betransmitted, and the quantity of the available code words for theadditional useful data is further limited.

[0035] In that context it must further be paid attention to, that asequence of code words, even if one sequences these one after another inthe worst possible conceivable arrangement, will in no case reach orachieve the triggering of the occupant safety devices.

[0036]FIG. 4 sketches the construction as well as the fragmentation ofthe entire data transmission protocol, whereby in this application, inresponse to a reset, whether this occurred by itself internally from thesensor assembly 1 or externally due to a control signal from the centralunit 3 or the read-out unit 5, at t0 first an initialization 1 and 2occurs, to which the acceleration data would be joined at t2 withtypical conventional acceleration sensor assemblies. Here, however,first the additional data signals are transmitted between t2 and t3,whereby this can give rise to no erroneous or faulty triggerings evenwith receivers without any recognition of this new data protocol, due tothe use of exclusively the sensor data range which is uncritical for theactivation unit of the occupant protection device, for the transmissionof the additional data. In this context, the additional data are packedinto n frames, which are transmitted in m repetitions, whereby thereceivers of the additional data can still reconstruct the additionaldata later due to these repetitions, even in the event of a shorttemporary interference on the sensor bus 4. For this, the framescomprise two 8-bit synchronization words and subsequently four datawords each of 8-bits, whereby in total only respectively 2-bit usefuldata are contained therein, and the other bits are used for start bitsand parity checking. Nonetheless, in a few hundred milliseconds,quantities of additional data larger than the sensor production data canbe transmitted over the existing transmission channel 4.

[0037] Respectively two of the code words 0, 3 and −3 are used for thesynchronization, whereby however the combinations (+3, +3) and (−3, −3)are excluded, in order to completely exclude the possibility that thecritical value range would be reached in an integration.

[0038] A frame can therefore maximally take on the following averagevalues: Sync Sync Data Data Data Data Sync Sync Data Data Data Data 1 21 2 3 4 ø 1 2 1 2 3 4 ø 0 0 −2 −2 −2 −2 −1.2 0 0 2 2 2 2 1.2 0 3 −2 −2−2 −2 −0.6 0 3 2 2 2 2 1.8 0 −3 −2 −2 −2 −2 −1.8 0 −3 2 2 2 2 0.6 3 −3−2 −2 −2 −2 −1.2 3 −3 2 2 2 2 1.2 −3 0 −2 −2 −2 −2 −1.8 −3 0 2 2 2 2 0.63 0 −2 −2 −2 −2 −0.2 3 0 2 2 2 2 1.8 ø Over Frame = −1.333 ø Over Frame= +1.333

[0039] In the average, with correspondingly distributed data bits, theadditional data signal is approximately free of steady components. Thus,an erroneous or faulty triggering can be excluded quite securely.

[0040] Moreover, a completely offset-free encoding of the additionaldata signal is possible, in that the additional data are transmittedonce normally and once inverted within a frame or scope that is to beagreed upon. For this purpose, of the reserved synchronization words“+3” and “−3”, one of these would be used as a signal for the respectiveinversion condition. If, for particular applications, still fewerdistinguishable code words are available in the uncritical value range,there additionally exists the possibility, in the limiting case, totransmit the corresponding additional data signals by a 1-bit sequenceformed by means of polynomial coding, and subsequently to reconstructthe additional data signals by means of the polynomial function from theuncritical value range that is, if applicable, to be interpreted asnoise.

[0041] Since the resets may also be triggered by the sensor assemblyitself, it cannot be excluded, that the transmission of the additionaldata would take place at a point in time at which the sensor data signalitself would take on safety critical values. Therefore, the datatransmission unit 13 of the acceleration sensor assembly of an occupantprotection system comprises a monitoring unit 15, which detects thepresent actual values of the sensor data signal s11 at least during thetransmission of the additional data signal s14, compares these presentactual values with prescribed nominal or rated values, and uponexceeding these nominal or rated values terminates the transmission ofthe additional data signals s14 and switches to the transmission of thesensor data signals s11.

1. Method for the transmission of a sensor data signal (s11) and anadditional data signal (s14) from a sensor assembly (1) to at least onereceiver of the sensor data signal (2) and one receiver of theadditional data signal (3, 5) through a common transmission channel (4),a) whereby a sensor (11) measures a quantity that is to be measured andgenerates a corresponding sensor data signal, b) the receiver (2) of thesensor data signal (s11) controls an application unit dependent on thesensor data signal, c) whereby the value range of the sensor data signal(x0-xn) comprises a value range (x0-x1) that is uncritical for thecontrol of the application unit, d) in response to a control signal(s3/s5/s15/s16/Uon), a data transmission unit (13) of the sensorassembly (1) at least temporarily for a short time transmits anadditional data signal (s14) instead of the sensor data signal (s11),whereby the value range (x0-x1) that is uncritical for the control ofthe application unit is used as the signal value range (y0-ym) for theadditional data signal (s14).
 2. Method according to claim 1, in which acertain value range (x0-x1) of the sensor data signal (s11) as a noiserange is attributable to a noise of the quantity to be measured as wellas of the sensor assembly, and the noise range (x0-x1) is used as thesignal value range (y0-ym) for the additional data signal (s14). 3.Method according to claim 1, wherein the receiver (2) of the sensor datasignal compares the sensor data signal with a threshold value (x2), andactivates the application unit only with a sensor data signal (s11)exceeding the threshold value (x2), whereby the value range below thisthreshold value (x0-x2) is used as the signal value range (y0-ym2) forthe additional data signal (s14).
 4. Method according to claim 1, sensorassembly (1) in an occupant protection system for motor vehicles, a) thesensor assembly (1) measures a safety relevant quantity and generates asensor data signal (s11) corresponding to the safety relevant quantity,b) at least one activation unit (2) of at least one occupant protectiondevice is provided, which receives the sensor data signals (s11) anddecides about the triggering of the occupant protection device(s)dependent on this sensor data signal (s11), whereby c) the sensor datavalue range (x0-xn) of the sensor data signal (s11) comprises asafety-uncritical value range (x0-x1), and the activation unit initiatesno activation of the occupant protection devices with sensor datasignals (s11) in this safety-uncritical value range (x0-x1), and d) inresponse to a prescribed control signal (s3, s5), the data transmissionunit transmits the additional data signal (s14) while using exclusivelythe safety-uncritical value range (x0-x1).
 5. Method according to claim4, whereby a) the sensor (11) is an acceleration sensor, the activationunit for the decision about the activation of the occupant protectiondevice(s) carries out an integration of the acceleration signal and acomparison of the acceleration integral signal with an activationthreshold and b) the safety-uncritical value range used for thetransmission of the additional data is determined so that the activationthreshold will in no case be reached even with an integration of thelargest values from the safety-uncritical value range.
 6. Methodaccording to one of the preceding claims, in which the data transmissionunit (13) comprises a monitoring unit (15), which detects the presentactual values of the sensor data signal (s11) at least during thetransmission of the additional data signal (s14), compares the presentactual values with prescribed nominal values, and upon exceeding thesenominal values terminates the transmission of the additional data signal(s14) and switches to the transmission of the sensor data signal (s11).7. Method according to one of the preceding claims, in which the datatransmission is achieved in digital code words, a) whereby among thecode words, a portion is provided for the transmission of controlsignals and the other portion is provided for the transmission of sensordata, b) of the code words used for the sensor data transmission, inturn a portion corresponds to sensor data that are uncritical for thecontrol of the application unit, and c) this portion of the code wordsis used for the transmission of the additional data.
 8. Method accordingto claim 5, whereby the transmission of the additional data is carriedout in a sequence of several code words and the code words of theadditional data are in turn divided into additional control data andadditional user data.
 9. Use of the method according to one of thepreceding claims for detecting sensor production data, especially anindividual sensor assembly number.
 10. Acceleration sensor assembly forgenerating an acceleration signal in an occupant protection system, a)whereby a signal value range (+127 to −127) is prescribed for the datatransmission, this signal value range is divided into a sensor datavalue range (+120 to −120) for the sensor data transmission and acontrol signal value range (+127 to +121 as well as −121 to −128), thatis distinguishable therefrom, for the transmission of control signalsfor controlling of the data transmission, b) at least one activationunit of at least one occupant protection device is provided, whichreceives the acceleration signals (s11) and decides about the triggeringof the occupant protection device(s) dependent on these accelerationsignals (s11), whereby c) the sensor data value range (+120 to −120) ofthe acceleration signal (s11) comprises a safety-uncritical value range(+3 to −3) and the activation unit initiates no activation of theoccupant protection devices with acceleration signals in thissafety-uncritical value range (+3 to −3), and d) in response to aprescribed control signal, the acceleration sensor transmits additionaldata (s14) while using exclusively the safety-uncritical value range (+3to −3).
 11. Acceleration sensor assembly according to claim 10, whichswitches from the transmission of the sensor data signal (s11) to thetransmission of the additional data (s14) in response to a command of aread-out unit (5) or of a central unit (3) of the occupant protectionsystem.
 12. Acceleration sensor assembly according to claim 10, which,in response to a reset that is externally generated from the centralunit (3) of the occupant protection system as well as in response to areset that is internally generated from the acceleration sensor assemblyitself, after an initialization signal, first transmits the additionaldata signal (s14) and subsequently switches (12) to the transmission ofthe sensor data signal (s11).